Abstract
BACKGROUND: The use of fourth-generation minimally invasive hallux valgus surgery with metaphyseal extra-articular transverse and Akin osteotomy, recently dubbed "META," is a new generation of minimally invasive surgical (MIS) technique and a recent focus of foot and ankle orthopaedic literature associated with good functional outcomes and low complication rates. Literature in orthopaedic trauma has indicated that 2 or 3 neocortices on postoperative radiographs are associated with high likelihood of union. In this study, we conducted a retrospective analysis to investigate the time to bony union for patients undergoing fourth-generation MIS hallux valgus repair as well as the relationship between intraoperative degree of first-metatarsal displacement and time to bony union. METHODS: We retrospectively analyzed 217 consecutive patients with moderate to severe hallux valgus who underwent fourth-generation MIS first distal metatarsal and Akin osteotomy between 2020 and 2023 and were followed for up to 1 year. Radiographic measurements included the scale of displacement between the proximal and distal portions of the first metatarsal as a percentage and the number of neocortical bridge formations at the osteotomy site. Postoperative weightbearing radiographs were recorded at 6 weeks, 3 months, 6 months, and 1 year to assess time to union and patient clinical outcomes. Two orthopaedic surgeons independently reviewed the radiographs to assess progression to bony union. Any discrepancy in analysis was resolved by a third-party clinician. Complete union was defined as the presence of at least 2 new cortical bridge formations on postoperative X-ray films. Patients were divided into 3 groups based on the percentage of shift on the first metatarsal head (≤50%, 51%-75%, ≥76%) for the purpose of our analysis. RESULTS: Union (≥2 cortices) was observed in 17%, 70%, and 90% of patients at 6 weeks, 3 months, and 6 months, respectively. At final follow-up (mean 13 ± 6.9 weeks), 92% achieved union. No significant differences in time to union were observed across metatarsal shift groups.Complications include 3 nonunions, 3 revisions, 16 cases that necessitated removal of hardware, 1 case of superficial wound infection, 1 case of deep wound infection, and 6 deformity recurrences. CONCLUSION: Time to union after META procedure typically occurred by 13 weeks, independent of shift magnitude. Surgeons may consider ≥2 cortices and absence of symptoms as sufficient indicators for advancing weightbearing. These findings may assist in patient counseling and postoperative planning.Level of Evidence: Level IV, retrospective case series.